(1) Field of the Invention
This invention relates to a gully arrangement which may form, for example, part of a drainage system.
(2) Description of Related Art
Conventional drainage systems, for example provided as a part of the infrastructure in residential and commercial areas, receive waste water, sewage and the like from residential premises and convey the waste to a sewage works or the like by way of a sewer which generally runs beneath a road. The drainage system includes a plurality of gullies which are conventionally provided at the side of a road or in another convenient location to receive rain water and transfer the same to the sewer. Such gullies are generally referred to as road gullies.
Under normal circumstances, such conventional drainage systems function adequately, but in the event of a flood there is often excess surface water which requires to drain away by way of the road gullies as well as increased flow through the sewer of the drainage system. If the flow through the sewer increases to a rate that the sewer is unable to accommodate, then backflow occurs and waste from the sewer flows back through the gully which may further increase the amount of surface water, but additionally may allow the escape of untreated sewage, which is not only inconvenient but also potentially harmful.
If a conventional drainage system is unable to cope in flood conditions, then it would be preferable to control the point or points in the drainage system where excess water and/or untreated sewage can escape, ideally at a location remote from residential or commercial areas.